<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>对单个单元格的内容垂直对齐</title>
</head>

<body>
    <table id="myTable" border="1">
        <tr>
            <td height="50px">第一个单元格</td>
            <td>第二个单元格</td>
        </tr>
        <tr>
            <td height="50px">第三个单元格</td>
            <td>第四个单元格</td>
        </tr>
    </table>
    <form>
        <input type="button" onclick="valignCell()" value="第一个单元格内容底部对齐">
    </form>
    <script>
        function valignCell() {
            var x = document.getElementById('myTable').rows[0].cells;
            x[0].vAlign = "bottom";
        }
    </script>
</body>

</html>